The state of the art of underground mine lighting devices is reviewed in the August 1974 issue of COAL AGE magazine, on pages 66-74, in an article by its senior editor, Nicholas P. Chironis, entitled "Underground mine lighting . . . A look at what's new in concepts and equipment".
Briefly, Federal legislation dating from 1969 has set minimum lighting standards for mines. To meet the standards, alot of mine lighting devices are needed. Four main types of mine lighting are competing for the market: fluorescent, sodium vapor, mercury vapor and incandescent, each type having a distinct range of uses for which it is more ideal. Some devices are made to mount on miner's caps, others variously on mine roofs, walls and the like, on portable stands or on mining machinery such as continuous miners, loading machines, cutting machines and roof bolting machines.
The present invention relates to those of the fluorescent type.
Present manufacturers of fluorescent type mine lighting devices include Control Products, Inc., of Beckley, West Virginia, and Ocean Energy, Inc., of Blairsville, Pennsylvania.
During the course of the preparation of this document, the present inventors have become aware of the following prior United States patents showing lighting devices.
______________________________________ Patentee U.S. Pat. No. Issue Date ______________________________________ Lester 2,794,113 May 28, 1957 Williams 2,807,710 September 24, 1957 Green 2,888,657 May 26, 1959 Oharenko 3,136,489 June 9, 1964 Oharenko 3,140,054 July 7, 1964 Hayasaka et al. 3,426,234 February 4, 1969 Phlieger, Jr. 3,564,234 February 16, 1971 ______________________________________